Water resistive barriers such as house wraps are can be effective in preventing the building enclosure from water such as wind driven rain, however, they are not necessarily effective air barriers. To be effective as an air barrier, materials must prevent the infiltration of air in addition to water. The use of air barriers has been increasing, due to their ability to improve durability, reduce energy and improve the indoor air quality. The Canadian NRC found that air movement is the major factor in transport of moisture through the building envelope. The transport of water vapor via air infiltration is 100 times more than that of vapor diffusion alone.
Air barriers can vary considerably in the degree of vapor permeance. Those barriers with a perm rating of <1 based on ASTM E96A are classified as impermeable. Perm ratings between 1 and 10 are semi-permeable, and those with perm ratings>10 are classified as permeable. Building design and location are two of the more important factors in determining which type of air barrier to use.
There are many forms of air barriers commercially available. One of the more widely recognized types are those which are mechanically fastened to the building, such as DuPont's Tyvek Commercial Wrap. This consists of a vapor permeable spun bond polyethylene film or membrane. To be an effective air barrier, mechanically fastened types must have every puncture, such as nail holes, and seams sealed. Having to seal every single nail or staple hole and seam is labor intensive and time consuming, but without such effort, they act as a water resistive barrier only. Another major drawback with the mechanically fastened types is lack of adhesion to the substrate. This free standing film type is easily torn from wind during installation or prior to covering the membrane with the building exterior. Also, given the stiffness of the material it is very noisy and difficult to handle in windy situations. The film may also tear due to negative pressure such as stack pressure. Thus, these mechanically fastened wraps have many drawbacks.
Fluid applied air barrier membranes, such as Grace Perm-A-Barrier VP and Perm-A-Barrier Liquid, are available and form an effective and durable air barrier. These types of barriers are fully adhered to the substrate which provides numerous benefits over the mechanical fastened type, such as ease of application, reduced tendency to tear under negative pressure, and no water infiltration. Fluid applied membranes can be either vapor permeable or impermeable. However, liquid spray applied product cannot be used in many situations, such as windy days, or close proximity to other buildings.
Self-adhered sheet air barrier membranes are available, such as Grace Perm-A-Barrier WM. This type of product is applied in peel and stick form and provide a very effective air barrier that seals nail and other punctures, bridges cracks and resists tearing. The majority of these types of sheets are composed of a polyethylene film and a very thick layer of asphaltic based adhesive. Given the nature of the adhesive, these types of membranes are impermeable to vapor.
There currently does not exist any contractor friendly, easy to install, vapor permeable air barrier membrane in sheet form. Blueskin Breather from Henry Corp. is a self-adhered vapor permeable transition membrane. This product is used mostly in applications transitioning from one product to another, such as a liquid applied to a flashing and is typically not used as a stand alone air barrier membrane. A particular drawback for this product is the membrane consists of a microporous laminated film which is very soft and weak. The membrane acts similar to that of a band aide and folds over onto itself causing wrinkles and sticking to itself. Thus, the product is not contractor friendly or easy to apply.
It is an object of the present invention to provide a self-adhered, vapor permeable, air barrier membrane that is easy to install.